Neutron-Neutron Cement Evaluation Tool for Heavy Casing Interference
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Solution Overview
Problem
Current cement evaluation technologies, such as sonic attenuation and ultrasonic impedance imaging, face challenges in deep water environments and regulatory compliance, particularly in distinguishing between heavy drilling mud and light cement, and are hindered by heavy casings, which affect measurement accuracy and sensitivity.
Innovation Solution
The implementation of neutron-neutron measurements using a tool with a neutron source and detectors to evaluate cement quality by comparing measured neutron counts and ratios, with dopants like boron or gadolinium in the cement to identify voids and poor cement quality, providing a quantitative and corroborative measure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If acoustic solutions (sonic attenuation, ultrasonic impedance imaging) are used for cement evaluation, then measurement capability is provided, but measurement precision deteriorates due to close impedance contrasts between heavy drilling mud and light cement, and heavy casings present additional barriers
Solution Approach 1:
The patent replaces acoustic measurement methods with neutron-based measurement. The neutron source emits neutrons that interact with the cement and drilling mud, and neutron detectors measure the neutron interactions. This substitution of the physical measurement principle (from acoustic to neutron) eliminates the interference problems caused by heavy casings and acoustic impedance contrasts between mud and cement.
Solution Approach 2:
The patent changes the measurement parameter from acoustic impedance to neutron interaction characteristics. By measuring neutron counts and neutron-to-gamma-ray ratios instead of acoustic signals, the method achieves sensitivity to cement quality that is not affected by the acoustic impedance contrasts or heavy casing interference.
2Measurement precision
If traditional acoustic measurement methods are used, then cement evaluation is possible, but sensitivity is insufficient to distinguish between heavy drilling mud and light cement
Solution Approach 1:
The patent replaces acoustic measurement with neutron measurement. Neutrons interact differently with cement containing dopants (like boron or gadolinium) compared to drilling mud, allowing clear differentiation. The neutron measurement system includes a neutron source and neutron detectors that measure neutron counts and ratios, providing sufficient sensitivity to distinguish cement from drilling mud regardless of mud weight.
Solution Approach 2:
The patent introduces dopants (such as boron or gadolinium) as intermediaries in the cement. These dopants have high neutron capture cross-sections, creating a distinct neutron interaction signature that differentiates cement from drilling mud. The dopants act as a mediator that enhances the contrast between cement and mud in neutron measurements.
3Reliability
If acoustic evaluation technologies are used, then cement quality assessment is provided, but reliability is reduced due to challenges in deep water environments and regulatory requirements
Solution Approach 1:
The patent replaces acoustic evaluation technologies with neutron-based evaluation. The neutron measurement system is not affected by the same environmental constraints that limit acoustic methods in deep water. The neutron source and detectors provide reliable measurements of cement quality (through neutron counts and neutron-to-gamma-ray ratios) that are not dependent on acoustic propagation conditions.
Solution Approach 2:
The patent changes the measurement parameter from acoustic properties to neutron interaction properties. This parameter change makes the measurement reliable in deep water environments where acoustic methods fail due to pressure, temperature, and regulatory constraints. The neutron measurement parameters (neutron counts, neutron-to-gamma-ray ratios) provide consistent and reliable cement quality assessment.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method offers improved sensitivity and depth of investigation, effectively flagging poor cement quality and allowing for remedial action, while being less affected by drilling mud weight and not using radioactive materials, thus enhancing zonal isolation and production efficiency.
Implementation Method 1
A neutron-neutron measurement is a measurement in which neutrons are generated from a source and neutrons are detected at a detector in response to the generation of neutrons
Data Source
AI summary
Various embodiments include apparatus and methods to conduct neutron-neutron measurements and to evaluate quality of cement between a casing and a formation. A tool can include a neutron source, a far detector, and a near detector, where the far detector and the near detector detect neutrons in response to activation of the neutron source. Measured counts of the detected neutrons can be compared with respect to expected counts of neutrons. From one or more comparisons, the quality of the cement can be evaluated. Additional apparatus, systems, and methods are disclosed.